The Timbers were tied for first in the league back in late June, but this time, being in first place is much more significant.

Kalif Alhassan scored just before halftime, and the Timbers defense continued its strong play with another shutout in the 1-0 win against archrival Seattle in front of a sellout crowd of 20,674 Sunday night at Jeld-Wen Field.

The Timbers (13-5-14, 53 points) vaulted into a tie with New York for first place in MLS after the win, which extended their unbeaten streak to six consecutive games (4-0-2). The victory didn't clinch a playoff berth for the Timbers, but they took another major step toward capturing their first-ever MLS playoff berth with two games remaining in the regular season.

"It's a big win," midfielder Will Johnson said. "We get closer to our goal of getting into the playoffs and get as high a seed as possible."

The Timbers will probably need to get one more point out of the final two games to clinch a playoff spot. But the Timbers have their sights set on not just earning a playoff berth, but winning the Western Conference title and winning the Supporters' Shield, awarded to the team with the best record in the regular season.

The Sounders (15-11-6, 51 points) lost their third consecutive game and are now winless in their last five games. They dropped to third place in the West, and have failed to clinch a playoff berth in four consecutive attempts.

The game was another typical physical and intense affair between the two longtime rivals, with the series dating back to 1975. However, with both teams entrenched in the playoff race — and its implications for berths, positioning, conference title and the Supporters' Shield — Sunday's game was the most important game since the two teams started competing against each other in MLS.

"That was the most intense atmosphere I've ever played in," Johnson said.

Both teams played as if their playoff lives depended on sealing a win. The Sounders, coming off two consecutive embarrassing losses, came into the game with a chip on their shoulder and decided to go physical on the Timbers.

The Sounders were called for 14 fouls, and the game reached a boiling point when Seattle center back Jhon Kennedy Hurtado fouled Darlington Nagbe, which led to plenty of pushing, shoving and trash-talking by players on both teams.

Away from the ball, Seattle midfielder Osvaldo Alonso and Johnson were jawing, and Alonso threw an elbow into Johnson's face. The assistant referee saw the exchange and Alonso was given a straight red card in the 74th minute, putting the Sounders a man down for the remainder of the game.

"If there's a fight, we're up for a fight," Portland coach Caleb Porter said. "This team is not soft. I thought they made it a fight and that was no problem for us. We're not going to back down."

The Timbers didn't back down, matched the Sounders blow for blow, but, unlike the Sounders, they didn't lose their cool.

Portland was called for nine fouls, but the only yellow card they received was for Alhassan's decision to take off his jersey during his goal celebration.

"Anytime you have a rivalry match like this and it means so much, especially with where both teams were in the standings, it's going to get chippy at times and it did," right back Jack Jewsbury said. "I thought we handled it well, we stuck up for each other, but at the same time, we didn't do anything that hurt the team."

The game was tight throughout, but the Timbers got the break just seconds before the end of the first half.

Jewsbury sent a cross into the Seattle penalty box area, and the Sounders couldn't adequately clear the ball. The ball bounced off Seattle defender DeAndre Yedlin and rolled straight to Alhassan. Alhassan lined up at the top of the box and blasted the shot past Seattle goalkeeper Marcus Hahnemann in the 45th minute.

"He seems to get big goals in these big games for us," Johnson said.

The Timbers defense rose to the occasion once again, posting its fourth shutout in the last six games and the fourth consecutive shutout at home. The Timbers also handed the Sounders their first shutout loss since July 13, a span of 14 consecutive games.

Portland did get a little lucky. The Sounders watched two shots - a header from Clint Dempsey and a deflected shot by Steve Zakuani - hit the crossbar. But goalkeeper Donovan Ricketts also produced another strong game, and the Timbers survived a siege when the ball was rolling dangerously in front of Portland's goal in the game's final moments.

"Your heart goes in your stomach," Porter said.

Despite the Sounders' near misses, Porter said he felt the game was the Timbers' to win. The win gave him his first regular-season victory over the Sounders.

Porter said he had thought about defeating the Sounders last October, just a couple of months after he had been named as coach.

"There's no reason why we would be inferior. There's no reason why we should be the little brother," Porter said. "We should be capable of beating the Sounders and it not being a miracle."